1. Field of the Invention
The present invention relates to a solid-state imaging device, method of manufacturing the same, and an electronic apparatus using the solid-state imaging device.
2. Description of the Related Art
In related art, as a solid-state imaging device used in a digital camera or a video camera, a CCD solid-state imaging device or CMOS solid-state imaging device are known. In these solid-state imaging devices, a light sensing portion is formed at each of a plurality of pixels which are formed in a two dimensional matrix shape, and signal electric charges are generated according to an amount of light received in the light sensing portion. In addition, the signal electric charges generated in the light sensing portion are transmitted and amplified, whereby an image signal is obtained.
In recent years, in the solid-state imaging device, in order to improve light collecting efficiency for light incident on the light sensing portion which has been reduced in size in response to a reduction in the size of the pixels, a spherical shaped on-chip micro lens or a gradient index lens is formed on a light incident side of the pixels (see, Japanese Unexamined Patent Application Publication Nos. 2004-304148 and 2008-10773). As a result, the light collecting efficiency for the light incident on the light sensing portion is improved, and sensitivity is improved.
A sectional configuration of a CCD solid-state imaging device using an on-chip micro lens in related art is illustrated in FIGS. 20A and 20B. As shown in FIG. 20A, the solid-state imaging device 100 of related art includes a substrate 101 on which the light sensing portion 102 is formed, a wiring layer 115 formed on the substrate 101, a color filter layer 109 formed on the wiring layer 115, and an on-chip micro lens 110.
The substrate 101 is constituted by a silicon substrate. The light sensing portion 102 is constituted by a photo diode, and a plurality of the light sensing portions in the form of a matrix is formed on a desired region of the substrate 101. In addition, a transmission channel portion 103 is formed through a read channel portion 105 on a region adjacent to the light sensing portion 102 on the substrate 101, and a transmission electrode 107 is formed on the wiring layer 115 which is on the read channel portion 105 and the transmission channel portion 103. The transmission electrode 107 is formed on a gate insulating film 106 formed on the substrate 101 above the read channel portion 105 and the transmission channel portion 103. Further, while not shown, in addition to the transmission electrode 107, desired wiring is formed through an insulating interlayer on the wiring layer 115.
In addition, one pixel is constituted by a region including the light sensing portion 102, the read channel portion 105 which is formed adjacent to the light sensing portion 102, and the transmission channel portion 103. The one pixel is separated from the adjacent pixel by a separation region 104. Further, the on-chip micro lens 110 is formed in the spherical shape, and the spherical on-chip micro lens 110 is used as a light collecting element.
In this configuration, incident light is collected by the spherical on-chip micro lens 110 and is incident on the light sensing portion 102. Signal electric charges are generated and accumulated according to incident light by photoelectric conversion in the light sensing portion 102. In addition, the signal electric charges accumulated in the light sensing portion 102 are read in the transmission channel portion 103 through the read channel portion 105 by applying a voltage to the transmission electrode 107 and transmitted in a vertical direction.
In this solid-state imaging device 100 in related art, the interface between air and the on-chip micro lens 110 has the second-highest refraction index of incident light, while the interface reflection of a substrate 101 including silicon has the highest refraction index. In cases where a periodic configuration such as the on-chip micro lens 110 is formed on the interface having a high reflectivity, when incident light L1 including parallel light beams is incident on the on-chip micro lens surface, as shown in FIG. 20B, light beams reflected on the on-chip micro lens surface of each pixel interfere with each other. Accordingly, a reflected diffraction light L2 is constituted by the interference of the reflected light.
As shown in FIG. 20B, when an outside element 116 such as a cover glass or a multilayer infrared cut filter is formed above the on-chip micro lens 110, the reflected diffraction light L2 is reflected by the outside element 116. In addition, a diffraction light L3 caused by the reflected diffraction light L2 further reflected by the outside element 116 is incident on the light sensing portion 102 again. The diffraction light L3 which enters in this manner is a cause of a ghost or flare. FIG. 21 schematically illustrates an image obtained when a subject having a high luminance is photographed with a solid-state imaging device 100 of the related art. As shown in FIG. 21, when a subject 121 having a high luminance is photographed, a ghost image 122 is photographed around the subject having a high luminance by the diffraction light L3 caused by the periodic configuration due to the on-chip micro lens 110 as described above.
In Japanese Unexamined Patent Application Publication No. 2008-66669, in order to suppress a ghost image, there is disclosed a technique in which the on-chip micro lens is formed with such a thickness as a ghost image hardly appears. However, as long as the interface between the air and the on-chip micro lens has a periodic configuration, it is difficult to dramatically suppress the occurrence of a flare or ghost.